1. Field of the Invention
This invention is directed to switch circuits, in general, and, more particularly, to a circuit device which permits a single switch circuit to be extended to a plurality of switch circuits.
2. Prior Art
There are many switching circuits known in the art. In addition, there are many programmable switching circuits and systems which are known in the art. One typical application of such circuits is in the field of irrigation control systems. These systems utilize a plurality of solenoid activated valves which are, typically, located at remote locations to control water flow at specified areas or zones. The valves are connected to electronic (or electro-mechanical) controller apparatus.
The controller, typically, includes a type of memory which can be programmed to selectively control the operation of the valves. In the primitive (or less sophisticated) systems, the programming can be controlled by various cams, gears, wheels or other mechanical or electromechanical equipment and the like. In the more sophisticated, space-age systems, the controller includes an electronic memory which can be programmed to perform very complex routines. That is, the various valves can be turned on and off for specific cycles, with selected operating durations, on a unique pattern of days, hours and so forth. Such systems are well known. One example, is U.S. Pat. No. 4,244,022 to T. L. Kendall and assigned to The Toro Company.
However, a major shortcoming of such systems is that an interruption (rupture) in the electrical interconnection wiring apparatus can render whole sections of the system inoperable. Unfortunately, a very expensive and usually disrupting repair project is required to correct the problem.
This repair may include pulling and replacing wires, as a minimum. Typically, however, the project includes digging, trenching, replacement and re-landscaping. Of course, if the digging and trenching take place through an existing parking lot, swimming pool, tennis court or similar improved area, the expense and inconvenience can be prohibitive.
Alternatively, odd ball installations with a number of independently operating sub-systems can be set up to replace the inoperative system portion. However, these unusual installations can provide an undesirably complex mosaic of a patchwork irrigation system.
Also, it is possible that battery operated controllers can be used to control the inoperative system portion. In addition to the complexity, this system is subject to battery failure, different clocking arrangements, overload of the water delivery system and the like.